Yes, I do from time to time. It makes me feel very girly.
Let me preface the following with this: I'm not a doctor. This isn't medical advice.
DON'T DO THIS. Seriously...Don't. It's likely not safe at all. YMMV. Consult a doctor if you have questions or concerns. Etc., Etc.
My biggest concern with using them has been the potential drying effect...after all, they are designed to be super absorbent. The last thing you want is it to stick to your guts on the inside because it dried out and stuck to a surface that is supposed to be wet. Then you'd be dealing with a potential for shredding and all all sorts of other nastiness.
To mitigate this, I have taken to using a lube-shooter (see image below) to insert a small amount of distilled water after inserting the tampon to cause the tampon to swell slightly and not be as absorbent. I carry a small Vera Bradley purse pouch in my computer bag (similar to image below....the Mini-trapeze cosmetics bag) which I can slip into my pocket to go to the loo. It contains a couple of ultrathin pads, a couple of tampons, and two baggies. One for the unused lube-shooters and small bottle of distilled water...the other for used shooters.
Then, I can change at work as needed. I find about 4 hours is the max I like to go, and it gives me a safety factor of being well below the generally recommended time. I consider it a good day if I can put one in in the morning, make it to lunch time for a change, then change again right after work. Some days there are additional changes during the day if needed.
Personally, I find that the light/slender or regular absorbancies work best for me for longer term wearing. Super, SuperPlus and Ultra ones tend to trigger my need to expel sooner than I'd like, unless I'm just playing around. For work day wearing, the smaller ones are my preference.
I also find that wearing them swelled up a bit from the water makes me a bit more aware of them. It's not really discomfort per se, but an awareness. I can wear the slender/lights with no discomfort at all, and they are almost unnoticable. I find the regular heightens the awareness a fair bit with occasional pangs of something that's not exactly pain, and a super causes some definitely abdominal discomfort when trying to suppress the urge to expel, which I like to imagine are a sissy's version of cramps, and endure with grace.
If I use an SuperPlus or Ultra, it's usually only a few minutes before my body is screaming to push it out. Fun for play time, but not really practical for discrete work-day wear.
Having them wet while inside you make withdrawal pretty easy. It just slides right out when you pull the string and push down internally.
I always give a good tug on the string before insertion just to make sure it's firmly attached. I also hold onto the string with one hand while deploying the lube-shooter to avoid accidentally pushing it up inside with the rest. I have also been known to use Astroglide water-based jelly lube in the lube shooter as well from time to time...though its usually a lot less easy to deal with than the water.